Missing 'Growing Pains' Star -- More Clues

A man who lived in the apartment building where Andrew Koenig lived turned up missing and ended up killing himself -- this according to a neighbor of Koenig's and a handyman who works in the building.

It's an eerie set of circumstances. We're told the downstairs neighbor took his life approximately two years ago.

But the handyman tells us he does not believe the "Growing Pains" star is dead, noting that Koenig gave a 30-day notice before moving out and got his security deposit back -- something someone suicidal might not do.

A neighbor tells us Koenig left a new pair of running shoes on his front doorstep with a note that read, "These will make a world of difference."

The landlord of Koenig's building also tells TMZ Andrew and his mom did not get along.